Oil gasification process



Feb. 16, 1937. A. JOHNSON ET AL OIL GASIFICATI-ON PROCESS Filed April25, 1953 v: [N VENTORS ALFRED c/Ofl/Vzf 01V CHARL :5 Elf/tMM/NGER ATTORNE Y 1 Patented Feb. 16, 1937 UNITED STATES PATENT 'OFFICE OILGASIFICATION PROCESS Application April 25, 1933, Serial No. 667,818

2 Claims.

This invention relates to the gasiflcation of hydrocarbons for theproduction of a combustible gas having a uniform preselected heatingvalue and specific gravity adapting it for the usual industrial anddomestic purposes. More particularly the invention involves anovel'process and apparatus-for the production, from hydrocarbon oils,orfrom other fluid hydrocarbons such as butane and propane,-of a richcombustible gas having a uniform preselected heating value within therange of from 500 to 1200 or more B. t. u. per cu. it.

According to a preferred form of the invention a combustible gas havinga heating value within the range from 800 to 1100 B. t. u. per cu. ft.is produced directly in a single generator shell,- thus rendering theinvention of great utility in connection with stand-by equipment used tohandle peak loads in systems transporting and distributing natural gasor similar combustible gases of high heating value.

In many respects this invention is similar to and embodies principles ofthe oil gasiflcation process described in the copending patentapplication of Alfred Johnson, Serial No. 561,354 filed September 5,1931 for Oil gasification process and apparatus. It essentially involvesthe utilization of a heat-insulated generator shell having therein arefractory filtering screen; and it provides during the heating cyclefor the alternate successive blasting of the generator screen upwardlyand downwardly for the purpose of consuming the carbon deposited thereinduring a prior gas-making cycle.

Among the more important objects of the present invention are: toprovide in novel manner in a process for manufacturing a richcombustible gas from hydrocarbons for supplying the heat requirements ofthe process in part by the controlled combustion of the carbon formed bythe cracking of hydrocarbons in an earlier gas-making cycle, and insubstantial'part by the regulated burning of a fuel mixture inconnection with the respective blasting of air upwardly and downwardlythrough a refractory generator screen; and to provide in novel mannerfor the uniform continuous production in a single shell unit of acombustible gas of high uniform heating value.

In its broadest scope, the invention involves the employment ofalternate up-and-down blast stages of a heating cycle through a highlyheated filter bed or screen of selectively sized refractory bodieswithin a gas generator, under conditions adapted to consume the carbonpreviously deposited within the screen during a previous gasmakingcycle.

The up-blast stage of the heating cycle preferably is divided into twounequal sub-stages, in the first of which blast air alone is used forcon- 5 suming the larger part of the carbon within the screen, andparticularly that lying in the lower portion of the screen. In thesecond sub-stage,

a regulated quantity of oil or other fluid hydrocarbon is burned in thepresence of air sufllcient not only to completely'consume the saidhydrocarbon but also preferably to burn a small additional quantity ofthe carbon present in the screen. The resultant combustion gases passingupwardly through the screen flow directly to the stack from thegenerator top.

During the down-blast stage, which preferably also is divided into twosub-stages, the first substage is carried out with an air blast alone,for burning substantially all of the remainder of the carbon present inthe screen. Thereafter in the second sub-stage a small amount of oil orother hydrocarbon is completely consumed with air introduced therewithin the generator above the screen,the hot combustion gases passingdownwardly through the refractory screen and thence directly to a stack.Preferably the heating operation is so carried out that the amount ofheat developed in the generator and the screen is approximately thatrequired to limit the extent of the cracking of hydrocarbons during thegasmaking cycle, to yield a generator gas having the heating valueindicated.

This invention is based in substantial part upon the discovery that byblasting a refractory generator screen successively or concurrently withair and with the highly heated combustion gases from the regulatedburning of a combustible fluid adjacent and within a refractory filteror generator screen, the blasting being divided into two separate stagesin one of which the screen is blasted upwardly,--and in the other ofwhich the screen is blasted downwardly,-it is possible to effect a. veryuniform heat distribution within the screen and adapt it for theproductionon a 5 commercial scale of a high B. t. u. gas-which incertain instances may have a heating value, close to that of naturalgas.

The general tendency for a rising hot zone to exist in any up-blastsystem is readily counteracted by the additional down-blast stage whichhelps to carry beat down into the refractory screen. Thus the top of thescreen may readily be maintained at a suitable temperature.

In the accompanying drawing, which illustrates a gas generatorillustrating one form of the invention; and

Fig. 2 is a vertical sectional-view taken through a gas generatorillustrating a second modification of the invention.

Referring now to the drawing, numeral ll designates a generator shellprovided with a suitable refractory lining l2. Mounted in the lower partof the generator is a. refractory arch 14 supporting thereon agas-permeable filter bed or screen I6 of considerable depth formed ofrefractory bodies,the latter of which may, if desired, be impregnated orcoated with, or may otherwise contain high-melting metals such asnickel, cobalt, vanadium, chromium or platinum, or alloys thereof,functioning as catalysts or reaction promoters for the water gasreaction between steam and carbon or hydrocarbons,--as well as beinghighly efllcient heat transfer agencies. The depth of the screen variesfrom around 2 ft. upwardly, depending upon the nature and size of therefractory material, and upon such conditions of operation as thetemperatures to be maintained in the screen, and the rate of flow of gastherethrough. While the size and shape of the refractory bodies may varyconsiderably,-it has been found that where employing a screen depth offrom 2 to 6 ft.,refractory bodies ranging in size from 1 x 1 x 1 toapproximately 3 x 1 x 1 /4 inches in size are eminently satisfactory. Itis preferred in the present invention that the uppermost layers ofrefractory bodies forming the screen be of somewhat larger size thanthose in the lower portion of the screen. These bodies may be oblong orround in form. The latter shape is particularly desirable in the upperlayers of the screen.

While the material composing the refractory screen preferably-is highlyheat-refractory, such as high alumina fire brick, carborundum, purealundum, and high silica refractories, adapted to withstand temperaturesabove 3000 F.,-other refractories adapted for use at lower temperaturesmay also be utilized in the screen.

The generator is provided with the' usual upper stack outlet l8 having astack valve 20. The base of the generator below the arch l4 also isdirectly connected with a gas outlet 22 having at its outlet end a stackvalve 24. The outlet 22 is connected to a wash box 26 by means ofgas-duct 26 having therein the valve 30. The wash box is provided withthe usual gas outlet 32.

For introducing steam into the base of the generator below the arch l4there is provided a valve-controlled steam line 34. For introducing amixture of fluid fuel and air 'to be combusted within the space 36 belowthe generator arch I4, there are provided respectively avalve-controlled fluid fuel line 38 and a valve-controlled air line 40.A valve-controlled steam line 42 provides for the introduction of steaminto the upper part of the generator above the refractory screen.Likewise the valve-controlled fluid fuel lines 44 and thevalve-controlled air lines 46 provide for the introduction into theupper part of the generator at a plurality of points above therefractory screen of combustible mixtures of fluid fuel and air forheating purposes during the heating cycle, and for the introduction tothe generator of make oil during each gas-making cycle.

A gas off-take bustle pipe 48 is directly connected by branch conduits50 with the generator interior at points about vertically midway of therefractory screen. The bustle pipe 46 is directly connected with thewash box through a conduit 62 havin therein a valve 53.

In the modification of the invention illustrated in Fig. 2, theconstruction in general is similar to that of Fig. 1,-the differencebeing that in the modification of Fig. 2, the generator space above therefractory screen has been provided with a refractory arch 60 havingsupported thereon refractory checkerwork 62. The steam, fluid fuel, andair connections 42, 44, and 46, lead into the interior of the generatorat points above the said checkerwork construction 62. There is thusdeflned between the top of the refractory screen and the lower part ofthe refractory arch 60, a combustion chamber 64 to which the oil orother fluid hydrocarbon is directly introduced through avalve-controlled line 66, and to which air or othercombustion-supporting gas may be introduced through valve-controlledconduit 68.

Provisions are made for observing at all times the temperature existingwithin the refractory screen, particularly in the lower part thereof,for ascertaining whether the down-flowing fluids in the gas-making cyclehave cooled the screen to a point where practical operation ceases. Forthis purpose a thermocouple 10 may be disposed in the refractory screenapproximately 4 inches from the'lower part thereof. A secondthermocouple I2 advantageously is located in the gas offtake line 22closely adjacent the generator.

In the preferred practice of the invention according to the modificationillustrated in Fig. 1,assuming that the generator is cold, and that therefractory screen is free from carbon deposits-the bottom burner isoperated by the proper adjustment of the fuel and air lines 38 and4ll,--the stack valve 20 being open and the valves 24, 30 and 53 beingclosed. The highlyheated combustion gases flow upwardly through therefractory screen, thereby heating the same more or less uniformly to ahigh gas-making temperature, after which they flow out through the stackiii. In certain instances in which substantial amounts of carbon arepresent in the screen, additional air is required to be introducedthrough line 40. However, in such instances there is a distinct tendencytowards uneven heating of the bed due to the non-uniform distribution ofcarbon therein. Therefore it is preferred to shorten the time of thefirst of the heating stages, in which the combustion gases and air flowupwardly, and to follow this up-stage with a down-stage whereinhighly-heated combustion gases are produced above the refractory screenby fuel and air introduced through lines 44-46, in amounts sufllcientfor complete combustion of the said fuel, with or Without additional airwhen substantial amounts of carbon are present in the screen. During thedown-blast stage, the stack valve 20 is closed and the stack valve 24 isopen.

After bringing the refractory screen to proper gas-making temperatureswithin the range of from 1450 to 1850 F., depending upon the desiredheating value of the gas to be produced, the stack valve 24 is closed,and oil or other fluid hydrocarbon is distributed upon the generatorscreen at suitable rates through lines 44, preferably together with asmall amount of steam around .2 pound per pound of oil introducedthrough line 42 for controlling the velocities of the gases through thegenerator. Immediately following the oil gasiflcation stage, steam aloneis introduced to the generator through line 42 a o'nmao iication stage.By its use carboncarried within gas-making cycle, if desired. In eitherinstance the screen is consumed, and screen temperatures and gasvelocities are controlled.

The hydrocarbon and steam may be introduced to the generatorconcurrently throughout the theresultant gases and vapors-produced inthe upper part of the generator by the high temperatures therein aredrawn downwardly through the refractory screen and flow through theoutlet conduit 22 and valve-controlled line 28 to the wash box, andthence to suitable purification apparatus and to storage. In the eventsubstantial quantities of carbon remain in the fuel bed from a previousgas-making cycle,-n'ot havmg been removed in the immediately precedingheating cyclef-the steam flowing downwardly through therefractory screenalone or with the oil gas not only reacts with the oil but also assistsin cleaning up the carbon in the screen and 30 facilitates temperaturecontrol therein.

Byseparating the gas-making cycle intotwo stages as described above, theordinary tendency for the hydrogen produced in the oilcracking stage toinhibit by mass action the wa- 3; ter gas reaction of the steam andcarbon of the refractory screen is reduced or'eliminated.

'Where a low gravity gas in the neighborhood of .6 gravity is desired,very small amounts of steam would ordinarily be usedwith the oil in themake cycle; although for a more efficient type of operation where asomewhat, higher gravity gas in the neighborhood of .7 is desired, it ispreferred to employ from about .3 1b. to 1 poundof steam per pound ofoil. While the 5 usual gas-making rates utilizing small amounts highergas-making rates.

of oil in the neighborhood of from .1 to .3 gallon per square foot ofcross-sectional area per minute may be employed, it is preferredaccording to the present invention, to utilize much A rate processing inexcess of .5 gallon and upwardly of 2.0 gallons of oil per square footof cross-sectional area of the screen per minute is more suitable.

When the generator and screen temperature has been reduced to a pointunsuitable for continued gasiflcation, the oil flow through lines 44 iscut off. The generator is then purged of oil vapors and gases by steamflowing downwardly through the same from the line 42, the gas going tothe wash box through line 28. The stack valve 20 is then opened, and ashort up-steam purge is used, the steam being introduced into the baseof the generator through line 34.

The generator is now ready for the succeeding c5 heating operation.Valve 30 is now closed; and

an up-blast of air is introduced into the cham-- ber 36 through theconduit 40, and flows through the carbon-carrying screen, the air beinggenerally employed in sufficient amount to burn the 70 major portion ofthe carbon present in the screen.

The heat thus developed raises the temperatures, particularly in theupper part of the screen and of the upper generator walls. Followingthis first part of the up-blast stage, a small, regu- 75 lated amount ofoil or other fluid fuel is introduced with the air through line llltheair being present in amount at least sufilcient to completelyfcombustthe said fuel and preferably to burn-an additional portion'of the carbonpresent in the screen. The up-blast heating stage is then discontinued,and air is introduced into the upper part of the generator through line46; the airflow through line 40 is then cut off, and the stack valve 24is opened. The stack valve 20 is then closed. By this method ofoperation it is possible to avoid the down steam purge following theup-blast stage of the heating cycle.

.' -.The air introduced through line is highly heated in the'generatortop and thence flows downwardly through the refractory screen,combusting a substantial amount of the remaining carbon present in theupper portion of the screen;-the resultant combustion gases flowingthrough gas outlet 22 and out the stack past valve 24.

Fuel is then introduced through lines upper part of the generator,together with air 44 to the flowing thereto through lines l6,-the airbeing out the screen temperatures. After this has been accomplished, thefiows of air and gas through conduits 44 and 15 are discontinued, andthe down-stream purge is carried out with steam introduced through linel2,the purged gases flowing out through stack valve 24. This down steampurge'may be avoided by continuing the flow of fuel through. lines 44after the air flow through lines 46 is cut oil. The stack valve 24 isthen closed, and the succeeding gas-making cycle is begun in the mannerdescribed.

In the above operations the heating value of the resultant gas isgenerally controlled by regulating the time of contact of the 011 withinthe high temperature refractory screen, and the temperature of therefractory bodies forming the screen. The latter may be determined bynoting the temperature of the gases leaving the screen, by means of athermocouple or the like which may be located in the gas ofitake 22,butpreferably within the refractory screen at a point from 4 to i 10 inchesabove the bottom of the screen.

The average gas temperatures within the screen when introducing thegas-making oil at a rate of .5 gallon per square foot of screencross-sectional area per minute as determined in actual operation aregiven below. These temperatures increase as the oil rate is increased:

Heating value Temp. of gases of gas leaving screen B. t. u. F.

While the quality of the oil, both as to its chemical constitution andits gravity, affect the above temperatures somewhat, the differencesinvolved are not critical. With lower molecularweight hydrocarbonshigher temperatures are required than with hydrocarbons of highermolecular weight, where the same fuel velocities through the generatorscreen are employed. Typical analyses of combustible gases made inaccordance with the present invention are given for an 800 and for a1000 B. t. 11. gas, in connection with the manufacture of which a smallamount of steam was supplied with the oil merely for oil-atomizationpurposes,i. e. about .1 pound of steam per pound of oil.

800-850 LOGO-1,050 Gas 13. t. u. range B.t.u. per B. t.u.per

cu. it on. it.

An important advantage of the above-described operation involving thecontrolled combustion of fuel above the refractory screen during thedownblast phase of the heating cycle resides in the fact that a verylarge quantity of the heat thus produced is absorbed and reradiated bythe upper side walls of the generator which greatly improves the heatingefliciency of the cycle and, during the subsequent gas-making cycle,facilitates the vaporization of the oil before it reaches the screen andconverts Conradson carbon (that is, low temperature cracking andvaporization carbon) into a finely divided form which is then carriedinto the screen rather than, as in prior practices, largely depositedupon the top. The particular type of screen or filter composed of smallrefractory bodies permits high oil rates within the generator many timesthose employed in the usual single shell oil generators now in use.Normally, fluid tar is produced within the refractory screen with littleor no lamp black.

In accordance with one form of the invention, the process is so operatedthat a complete set of heating and gas-making cycles occupies betweenand minutes. This period, however, may be lengthened to 10 to minutes,or even longer. The rich combustible gas issuing from the refractoryscreen during the various portions of each gas-making cycle will thenhave a greater range of heating values than where smaller periods areemployed, because in the former instance the refractory screen andgenerator will be carried to a higher temperature prior to beginning thegasmaking cycle; and during the latter part thereof the screen will bequenched to a lower temperature where the shorter periods are employed.The longer the cycle,-the greater the quantity of carbon deposited uponthe screen during the first part of the gas-making step; and this isavailable for reheating the screen upon the succeeding heating cycle.

In many cases, such as that mentioned immediately above, the temperatureof the refractory screen at the beginning of the make cycle may be sohigh as to produce a cracked gas of too low a B. t. u. value in theevent that all of the oil vapors and other fluids are passed completelythrough the refractory screen. In such instances, it is within the scopeof the invention to ing cycle continues and the refractory screen Ibecomes progressively cooler, the heating value of the offcoming gasesmay be controlled by reducing the percentage of the gases flowing to thewash box past valve 53, or by closing this valve completely.

In view of the fact that a large portion of the energy required for thepractice of the process is of the nature of heat utilized in thevaporization of the oil before-and as it enters the screen, a form ofseries'heating of the generator and screen can be undertaken preferablyutilizing the modification 'of apparatus illustrated in Fig. 2.

In this form of the invention, the gas-making cycle is similar to thatpreviously described. The up-blast stage of the heating cycle isperformed in manner similar to that already described in connection withthe other modification of the invention; and the highly heatedcombustion gases serve to heat not only the refractory screen but alsoin the case of the apparatus of Fig. 2, the checker-work construction 62in the upper part of the generator. In this up-blast stage, theadditional regulated burning within the chamber 84 of a combustiblemixture of fluid fuel and air introduced through the lines 66 and 68 ofFig.2, preferably is carried out for the purpose of highly heating thecheckerwork 62. This mixture may be replaced in certain instances bysecondary air introduced into chamber 64 through lin! 68 or through line46 (Fig. 1).

In the preferred form of the down-blast stage of the heating cycle,combustion air is introduced above the checker-work construction 62 and,in passing downwardly is preheated by the latter,after which it mixes inchamber 64 with a combustible mixture introduced through lines 66, 68.The resultant combustion products pass downwardly through the screen,and thence to the stack.

In a slightly different form of operation, during the down-blast stageof the heating cycle, combustion air, followed by a combustible mixtureof fluid fuel and air are successively introduced above the checker-workconstruction 62 thereby producing heat, a substantial amount of which isabsorbed within the checker-work construction and the remainder of whichthen flows downwardly through the refractory screen in the usual manner,and thence to the stack.

Under certain conditions, a regulated amount of a combustible mixture offluid fuel and air concurrently is introduced above the screen throughthe respective lines 66 and 68, and to the central combustion chamber 64to further facilitate the heating of the chamber 64 and the refractoryscreen I6.

In the immediately following gas-making cycle, steam introduced throughthe line 42 is superheated in its passage through the checker-work 62;and later, in its passage through the chamber 64, this superheatfacilitates the vaporization and cracking of the hydrocarbon introducedat that time upon the refractory screen through the lines 66.

It is within the scope of the present invention to employ in either ofthe stages of the heating cycle any suitable combustible mixture ofcombustible fluid and a. combustion-supporting fluid.

These combustible mixtures preferably are overventilated (that is,containing an excess of combustion supporting fluid) so as to beeffective for substantially reducing the amount of carbon in therefractory screen by reaction therewith.

In the gas-making cycle, while it is preferred to employ hydrocarbonoils,-particularly those around the gravity of fuel oil or slightlyheavier, and having A. P. 'I. gravities of 12 to 18 the invention is inno wise limited to the use of these oils. On the contrary it is withinthe scope of the invention to employ a wide variety of liquid andgaseous hydrocarbons, including natural gas, refinery gases, butane,propane, and the like.

In instances of the use of each hydrocarbon or mixture-containinghydrocarbons it is only essential to supply, by the controlledcombustion of fuel in the manner indicated, that portion of the heatrequired for the cracking of hydrocarbons during the gas-making cyclewhich is not supplied by the controlled combustion of the carbon and tarformed in the screen during an earlier gas-making cycle; and to soregulate the direction of flow of the resultant hot combustion gases inthe generator as to maintain the refractory screen throughout at anapproximately uniform selected temperature which,- at the highgas-making rates generally employed with the corresponding short timesof contact of the gases with the high-temperature refractoryscreen,--insures an amount of cracking providing commercial yields ofthe desired high B. t. u. value gas.

Because of the simplicity of the apparatus construction, the inventionhas great commercial value for use both as standby and base loadequipment in industrial gas-making plants, and particularly thoserequired to supply rather widely variable seasonal or other deniandswhere the maximum gas-making demand upon the plant is felt onlyoccasionally; but where the equipment cost is high.

The invention is not limited to the treatment of the fluid hydrocarbonsnamed: but on the other hand is equally applicable to the production ofa rich combustible gas from other hydrocarbons such as natural gas andrefinery gases.

The invention is susceptible of modification within the scope of theappended claims.

We claim:

1. In a cyclic process for making combustible gas wherein during a gasmake period hydrocarbons are cracked by passing the same through a deepcarbon filtering bed of highly heated refractory pieces with resultantdeposition ofcarbon on the surfaces of the refractory which carbon isburned during a subsequent air blast period, the steps comprisingsuccessively blasting air vertically in both directions through the bedbetween make periods, burning fluid fuel within the bed during the blastperiod, controlling the amount of air employed during the blast periodto an amount approximately sufficient to burn the said fluid fuel and toconsume the carbon deposited within the bed during the preceding makeperiod, withdrawing combustion gases produced during the upblast stagefrom the upper part of the generator above the screen, concurrentlyburning additional fluid fuel above the said screen, -regenerating heatfrom the combustion gases at points in their path above the screen, andutilizing heat thus regenerated for preheating air for use in asubsequent down blast stage of the heating cycle and for preheatingsteam for use in a subsequent gas making period.

2. In a cyclic process for making combustible gas wherein during a gasmake period liquid hydrocarbons are cracked by passing the samedownwardly through a deep carbon filtering screen of small highly heatedrefractory pieces, with resultant formation of gas and deposition ofcarbon on the surfaces of the refractory which carbon is burned during asubsequent air blast period, the steps comprising successively blastingair vertically in both directions through the screen between makeperiods, burning fluid fuel within the screen during the blast period,controlling the amount of air employed during the blast period to anamount approximately suffi cient to burn the said fluid fuel and toconsume the carbon deposited within the screen during the preceding makeperiod, and regulating the calorific value of the gas produced duringthe make period by withdrawing a regulated amount of the make gasperipherally from the vertical midportion of the screen, whilewithdrawing the remaining portion of the make gas from below the screen.

CHARLES E. HEMMINGER.

ALFRED JOHNSON.

